The present invention relates generally to lawn mowers having an engine powered rotary cutting blade. More particularly, this invention pertains to powered lawn mowers wherein the rotary cutting blade is mechanically coupled to the engine using a belt-driven quill assembly.
Quill assemblies are commonly used in lawn tractors and other powered lawn mowers to connect to an engine powered v-belt drive and transmit power through a vertical jackshaft to a mower blade. Such quill assemblies will typically have a bearing at the top of the assembly near the v-belt pulley and at the bottom of the assembly near the blade. During use of the mower, the top bearing is exposed to water damage and the bottom bearing is affected by debris thrown upward from the blade. Also, the spacing of these bearings must be carefully controlled so that the pulley and blade are fixed in the proper vertical position. This vertical positioning is often provided in the prior art by the use of separate spacers. Unfortunately, the use of spacers increases the risk that the bearings will be side pre-loaded during assembly of the mower, making them susceptible to premature failure.
Another problem with conventional quill assemblies is that the jackshafts often have a uniform diameter along their length. When the mower blade strikes a foreign object, a large bending force is transmitted to the jackshaft. When the jackshaft bends, the housing can crack or fracture and pieces can be thrown as dangerous projectiles from the mower.
Prior art quill assemblies are also difficult to assemble because the jackshaft and blade adapter would easily fall out of the assembly during production of the mower.
What is needed, then, is a quill assembly for a lawn mower that provides protection against water and debris entering the bearings, that does not require separate spacers to position the pulley and blade, that resists damage caused by bending of the jackshaft, and is easy to assemble into a lawn mower.
One object of the present invention is to provide a quill assembly that incorporates auxiliary sealing components for the bearings at the pulley and blade ends of the assembly.
Another object of the invention is to eliminate the need for using spacers in a quill assembly to position the bearings, blade and pulley.
A further object of the invention is to prevent axial pre-loading of the quill assembly bearings during assembly of the lawnmower.
Yet another object of the invention is to provide a quill assembly that is easy to install into a lawnmower.
These and other objects are achieved by a quill assembly for use in a lawn mower for transferring power from a belt drive connected to a pulley at the top of the assembly to a rotating cutting blade connected at the bottom of the assembly. The quill assembly includes a housing having a central bore extending from a top of the housing to a bottom of the housing, a bottom bearing supported by a seat within a bottom bearing bore at the bottom of the housing, a top bearing having an outer ring supported by a seat within a top bearing bore at the top of the housing and an inner ring supported by a shoulder on a jackshaft, a jackshaft having an enlarged center portion positioned within the bore of the housing and supported for rotary operation by shouldering the top and bottom bearing inner rings, with the blade end of the jackshaft extending from the bottom of the housing and a pulley end of the jackshaft extending from the top of the housing, a pulley adapter adjoining the top of the housing, the pulley adapter having a center section with an central bore positioned around the pulley end of the jackshaft in a slip-fit engagement and an adjacent outer section with a flexible outer lip extending over and sealing the top of the housing, and a blade adapter recessed into an adapter counter-bore at the bottom of the housing, the blade adapter having a central splined bore surrounding the blade end of the jackshaft.
In one embodiment of the invention, the blade adapter counter-bore is larger than the bottom bearing bore such that the blade adapter engages the housing to form a seal for the bottom bearing.
Preferably, the quill assembly also includes an annular groove formed around the housing proximate the top of the housing, the groove receiving the outer lip of the pulley adapter.
The top bearing bore has a diameter sized to define a slip fit engagement between the top bearing and the top bearing bore whereby the top bearing floats within the top bearing bore. The center portion of the jackshaft has a larger diameter than the blade and pulley ends to form top and bottom shoulders on the jackshaft that support respective inner rings of the top and bottom bearings.
The top and bottom shoulders on the jackshaft are positioned at predefined locations along the jackshaft such that the top and bottom bearings are supported at predefined vertical positions along the jackshaft without the use of separate bearing spacers. The center section of the pulley adapter extends upwardly from the top of the housing to support the pulley at a pre-defined vertical position above the assembly without the use of a separate pulley spacer.